1. Field of the Invention
The present invention relates to an information recording disk drive unit, and in particular to a micro-actuator of the disk drive unit with electric spark preventing structure and manufacturing method thereof.
2. The Prior Arts
Disk drives are information storage devices that use magnetic media to store data. The structure of a conventional disk drive is illustrated in FIG. 1. The conventional disk drive comprises a casing 701 containing a set of circular disks 702 each having a surface on which a magnetic coating is provided for forming a plurality of concentric tracks (not shown). The disks 702 are mounted on a spindle motor 703 that selectively spins the disks 702. A drive arm 704 is arranged in the casing 701 and is controlled by a voice-coil motor (VCM) 707 to drive a head gimbal assembly (HGA) 705 with respect to the disks 702, whereby a micro-actuator with a head slider received therein carried by the HGA 705 is movable across the surface of the disk 702 from track to track for reading data from or writing data to the disk.
However, because the large inertia of the VCM 707, the slider cannot attain a quick and fine position control that limits the servo bandwidth of the disk drive, That affects the capacity increasing of the HDD.
In order to solve the above-mentioned problem, a piezoelectric (PZT) micro-actuator is employed to modify the displacement (off-track) of the slider. The PZT micro-actuator has higher frequency components than the VCM and corrects the displacement of the slider in a much smaller scale to compensate for errors caused by the VCM. The PZT micro-actuator enables the head work well in a smaller recording track width, thereby increasing the value of “tracks per inch (TPI)” by 50% of the disk drive unit and thus increasing disk surface recording density and drive performance of the disk drive unit. Such as reduces the head seeking and settling time.
Referring to FIG. 2a, a conventional HGA 277 comprises a suspension 213 to load a PZT micro-actuator 205 with a slider 203 received therein. The suspension 213 comprises conductive traces 210a, 210b that are connected to the slider 203 and the PZT micro-actuator 205, respectively.
Referring to FIG. 2b, the PZT micro-actuator 205 comprises a metal frame 230 having two side arms 211, 212, a top support arm 215 and a bottom support arm 216 respectively connected with the top ends of the two side arms 211, 212. The two side arms 211, 212 are in parallel with and spaced from each other a distance adapted to hold a slider 203 therebetween that is mounted on the top support arm 215. The top support arm 215 and the bottom support arm 216 are in parallel with each other; and the top support arm 215 is in parallel with a surface of the slider 203. Two PZT elements 207, 208 are respectively mounted by for example epoxy on outside surfaces of the two side arms 211, 212 for actuation. Also referring to FIGS. 2d, the two PZT elements 207, 208 each has a multi-layered structure of alternately laminating piezoelectric material layers 225 and two electrodes 223, 224. Two electrical contact pads 220, 221 are coupled to the electrodes 223, 224, respectively.
Referring to FIGS. 2c, the PZT micro-actuator 205 is coupled to a tongue (not labeled) of the suspension 213 of the HGA 277 on the bottom support arm 216 by epoxy or laser welding. A plurality of electrical connection balls 209a, such as gold ball bonding (GBB) and solder ball bonding (SBB), on each one side of the PZT elements 207, 208 connect the electrical contact pads 220, 221 of the PZT elements 207, 208 laminated on the side arms 211, 212 of the micro-actuator 205 to the conductive traces 210a. In addition, metal balls 209b, such as GBB and SBB, electrically connect the slider 203 to the conductive traces 210b for electrical connection of the read/write transducers. When an actuating power is applied through the conductive traces 210a, the PZT elements 207, 208 on the side arms 211, 212 will expand or contract, causing the side arms 211, 212 to bend in a common lateral direction. The bending causes a shear deformation of the metal frame 230. Its rectangular shape becomes approximately a parallelogram. The slider 203 undergoes a lateral translation because the slider 203 is attached to the moving side (support arm 215) of the parallelogram. Thus, a fine head position adjustment can be attained.
However, referring to FIG. 3, when a voltage is input to operate the micro-actuator 205, an electric spark 303 will happen since the bottom surfaces of the PZT elements 207, 208 are electrodes with an operate voltage and the metal frame 230 is a common ground while the bonding epoxy is very thin (less than 5 μm). This is why the electric spark problem happens between the metal frame 230 and the PZT elements 207, 208 when the environment condition changes during the micro-actuator operation. Hence, it is desired to provide a micro-actuator of the disk drive unit with electric spark preventing structure and a manufacturing method thereof.
In addition, to get an enough stiffness to support the slider during the flying, it is needed for the frame to have an enough thickness. This will cause a difficulty for the frame manufacturing for example the shape etching or molding, and the frame forming. The thick frame material will make the manufacturing process difficult and the cost expensive. Hence, the present invention is to provide with a design to reduce the frame thinner and get similar performance, in addition, to achieve a lower cost and a flexible manufacturing process.